Neurons in the fusiform gyrus are fewer and smaller in autism
ABSTRACT Abnormalities in face perception are a core feature of social disabilities in autism. Recent functional magnetic resonance imaging studies showed that patients with autism could perform face perception tasks. However, the fusiform gyrus (FG) and other cortical regions supporting face processing in controls are hypoactive in patients with autism. The neurobiological basis of this phenomenon is unknown. Here, we tested the hypothesis that the FG shows neuropathological alterations in autism, namely alterations in neuron density, total neuron number and mean perikaryal volume. We investigated the FG (analysing separately layers II, III, IV, V and VI), in seven post-mortem brains from patients with autism and 10 controls for volume, neuron density, total neuron number and mean perikaryal volume with high-precision design-based stereology. To determine whether these results were specific for the FG, the same analyses were also performed in the primary visual cortex and in the cortical grey matter as a whole. Compared to controls, patients with autism showed significant reductions in neuron densities in layer III, total neuron numbers in layers III, V and VI, and mean perikaryal volumes of neurons in layers V and VI in the FG. None of these alterations were found in the primary visual cortex or in the whole cerebral cortex. Although based on a relatively small sample of post-mortem brains from patients with autism and controls, the results of the present study may provide important insight about the cellular basis of abnormalities in face perception in autism.
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ABSTRACT: Autism is a heterogeneous behaviorally defined neurodevelopmental disorder. It is defined by the presence of marked social deficits, specific language abnormalities, and stereotyped repetitive patterns of behavior. Because of the variability in the behavioral phenotype of the disorder among patients, the term autism spectrum disorder has been established. In the first part of this review, we provide an overview of neuropathological findings from studies of autism postmortem brains and identify the cerebellum as one of the key brain regions that can play a role in the autism phenotype. We review research findings that indicate possible links between the environment and autism including the role of mercury and immune-related factors. Because both genes and environment can alter the structure of the developing brain in different ways, it is not surprising that there is heterogeneity in the behavioral and neuropathological phenotypes of autism spectrum disorders. Finally, we describe animal models of autism that occur following insertion of different autism-related genes and exposure to environmental factors, highlighting those models which exhibit both autism-like behavior and neuropathology.09/2013; 2013:731935. DOI:10.1155/2013/731935
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ABSTRACT: Neurophysiology and optical imaging studies in monkeys and functional magnetic resonance imaging (fMRI) studies in both monkeys and humans have localized clustered neural responses in inferotemporal cortex selective for images of biologically relevant categories, such as faces and limbs. Using higher resolution (1.5 mm voxels) fMRI scanning methods than past studies (3–5 mm voxels), we recently reported a network of multiple face- and limb-selective regions that neighbor one another in human ventral temporal cortex (Weiner and Grill-Spector, Neuroimage, 52(4):1559–1573, 2010) and lateral occipitotemporal cortex (Weiner and Grill-Spector, Neuroimage, 56(4):2183–2199, 2011). Here, we expand on three basic organization principles of high-level visual cortex revealed by these findings: (1) consistency in the anatomical location of functional regions, (2) preserved spatial relationship among functional regions, and (3) a topographic organization of face- and limb-selective regions in adjacent and alternating clusters. We highlight the implications of this structure in comparing functional brain organization between typical and atypical populations. We conclude with a new model of high-level visual cortex consisting of ventral, lateral, and dorsal components, where multimodal processing related to vision, action, haptics, and language converges in the lateral pathway. Electronic supplementary material The online version of this article (doi:10.1007/s00426-011-0392-x) contains supplementary material, which is available to authorized users.Psychological Research 12/2011; 77(1). DOI:10.1007/s00426-011-0392-x · 2.47 Impact Factor
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ABSTRACT: Self-awareness is a specific type of autoclitic discriminative behavior and inferential generalization to similar performances exhibited by other people. Brain imaging findings take on special importance within behavior analysis when they indicate that dysfunctions in these areas are related to differential effects of our interventions, with some acquiring substantially typical self-awareness skills and others failing to do so. It appears that those individuals whose brain dysfunctions are limited to these areas, and are not part of more generalized brain abnormalities, are amenable to substantial acquisition of those most basic of human skills called self-awareness, whereas individuals with more generalized brain dysfunction are not so disposed. Through a combination of less or more effective teaching contingencies during childhood, and degrees of dysfunction of those brain structures, some children grow up lacking self-reflective abilities and self-insight, whereas others are extraordinarily astute at those capacities. Among children with autism spectrum disorders who lack those skills due to abnormal brain development, approximately half of them can acquire those skills, at least to some degree through the use of effective, intensive, early behavior therapy methods.The Behavior analyst / MABA 01/2008; 31(2):137-44. · 1.08 Impact Factor